Why is SaaS and cloud computing so important?

Software-as-a-Service (SaaS) is the cornerstone of FinTech as it allows for 'pay-as-you-go' software models. In the bad old days, a business would need to pay hundreds of thousands (and sometimes millions) of dollars for an enterprise license for a core product like Oracle database or IBM Websphere. Times have changes and now small companies can grow without the same financial constraints by 'renting' the software in the cloud based on their level of usage.